
/*
 * Copyright (C) Nginx, Inc.
 * Copyright (C) Valentin V. Bartenev
 * Copyright (C) 2015 Vlad Krasnov
 */


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>


typedef struct
{
    uint32_t code;
    uint32_t len;
} ngx_http_v2_huff_encode_code_t;


static ngx_http_v2_huff_encode_code_t ngx_http_v2_huff_encode_table[256] = {
    {0x00001ff8, 13}, {0x007fffd8, 23}, {0x0fffffe2, 28}, {0x0fffffe3, 28},
    {0x0fffffe4, 28}, {0x0fffffe5, 28}, {0x0fffffe6, 28}, {0x0fffffe7, 28},
    {0x0fffffe8, 28}, {0x00ffffea, 24}, {0x3ffffffc, 30}, {0x0fffffe9, 28},
    {0x0fffffea, 28}, {0x3ffffffd, 30}, {0x0fffffeb, 28}, {0x0fffffec, 28},
    {0x0fffffed, 28}, {0x0fffffee, 28}, {0x0fffffef, 28}, {0x0ffffff0, 28},
    {0x0ffffff1, 28}, {0x0ffffff2, 28}, {0x3ffffffe, 30}, {0x0ffffff3, 28},
    {0x0ffffff4, 28}, {0x0ffffff5, 28}, {0x0ffffff6, 28}, {0x0ffffff7, 28},
    {0x0ffffff8, 28}, {0x0ffffff9, 28}, {0x0ffffffa, 28}, {0x0ffffffb, 28},
    {0x00000014, 6},  {0x000003f8, 10}, {0x000003f9, 10}, {0x00000ffa, 12},
    {0x00001ff9, 13}, {0x00000015, 6},  {0x000000f8, 8},  {0x000007fa, 11},
    {0x000003fa, 10}, {0x000003fb, 10}, {0x000000f9, 8},  {0x000007fb, 11},
    {0x000000fa, 8},  {0x00000016, 6},  {0x00000017, 6},  {0x00000018, 6},
    {0x00000000, 5},  {0x00000001, 5},  {0x00000002, 5},  {0x00000019, 6},
    {0x0000001a, 6},  {0x0000001b, 6},  {0x0000001c, 6},  {0x0000001d, 6},
    {0x0000001e, 6},  {0x0000001f, 6},  {0x0000005c, 7},  {0x000000fb, 8},
    {0x00007ffc, 15}, {0x00000020, 6},  {0x00000ffb, 12}, {0x000003fc, 10},
    {0x00001ffa, 13}, {0x00000021, 6},  {0x0000005d, 7},  {0x0000005e, 7},
    {0x0000005f, 7},  {0x00000060, 7},  {0x00000061, 7},  {0x00000062, 7},
    {0x00000063, 7},  {0x00000064, 7},  {0x00000065, 7},  {0x00000066, 7},
    {0x00000067, 7},  {0x00000068, 7},  {0x00000069, 7},  {0x0000006a, 7},
    {0x0000006b, 7},  {0x0000006c, 7},  {0x0000006d, 7},  {0x0000006e, 7},
    {0x0000006f, 7},  {0x00000070, 7},  {0x00000071, 7},  {0x00000072, 7},
    {0x000000fc, 8},  {0x00000073, 7},  {0x000000fd, 8},  {0x00001ffb, 13},
    {0x0007fff0, 19}, {0x00001ffc, 13}, {0x00003ffc, 14}, {0x00000022, 6},
    {0x00007ffd, 15}, {0x00000003, 5},  {0x00000023, 6},  {0x00000004, 5},
    {0x00000024, 6},  {0x00000005, 5},  {0x00000025, 6},  {0x00000026, 6},
    {0x00000027, 6},  {0x00000006, 5},  {0x00000074, 7},  {0x00000075, 7},
    {0x00000028, 6},  {0x00000029, 6},  {0x0000002a, 6},  {0x00000007, 5},
    {0x0000002b, 6},  {0x00000076, 7},  {0x0000002c, 6},  {0x00000008, 5},
    {0x00000009, 5},  {0x0000002d, 6},  {0x00000077, 7},  {0x00000078, 7},
    {0x00000079, 7},  {0x0000007a, 7},  {0x0000007b, 7},  {0x00007ffe, 15},
    {0x000007fc, 11}, {0x00003ffd, 14}, {0x00001ffd, 13}, {0x0ffffffc, 28},
    {0x000fffe6, 20}, {0x003fffd2, 22}, {0x000fffe7, 20}, {0x000fffe8, 20},
    {0x003fffd3, 22}, {0x003fffd4, 22}, {0x003fffd5, 22}, {0x007fffd9, 23},
    {0x003fffd6, 22}, {0x007fffda, 23}, {0x007fffdb, 23}, {0x007fffdc, 23},
    {0x007fffdd, 23}, {0x007fffde, 23}, {0x00ffffeb, 24}, {0x007fffdf, 23},
    {0x00ffffec, 24}, {0x00ffffed, 24}, {0x003fffd7, 22}, {0x007fffe0, 23},
    {0x00ffffee, 24}, {0x007fffe1, 23}, {0x007fffe2, 23}, {0x007fffe3, 23},
    {0x007fffe4, 23}, {0x001fffdc, 21}, {0x003fffd8, 22}, {0x007fffe5, 23},
    {0x003fffd9, 22}, {0x007fffe6, 23}, {0x007fffe7, 23}, {0x00ffffef, 24},
    {0x003fffda, 22}, {0x001fffdd, 21}, {0x000fffe9, 20}, {0x003fffdb, 22},
    {0x003fffdc, 22}, {0x007fffe8, 23}, {0x007fffe9, 23}, {0x001fffde, 21},
    {0x007fffea, 23}, {0x003fffdd, 22}, {0x003fffde, 22}, {0x00fffff0, 24},
    {0x001fffdf, 21}, {0x003fffdf, 22}, {0x007fffeb, 23}, {0x007fffec, 23},
    {0x001fffe0, 21}, {0x001fffe1, 21}, {0x003fffe0, 22}, {0x001fffe2, 21},
    {0x007fffed, 23}, {0x003fffe1, 22}, {0x007fffee, 23}, {0x007fffef, 23},
    {0x000fffea, 20}, {0x003fffe2, 22}, {0x003fffe3, 22}, {0x003fffe4, 22},
    {0x007ffff0, 23}, {0x003fffe5, 22}, {0x003fffe6, 22}, {0x007ffff1, 23},
    {0x03ffffe0, 26}, {0x03ffffe1, 26}, {0x000fffeb, 20}, {0x0007fff1, 19},
    {0x003fffe7, 22}, {0x007ffff2, 23}, {0x003fffe8, 22}, {0x01ffffec, 25},
    {0x03ffffe2, 26}, {0x03ffffe3, 26}, {0x03ffffe4, 26}, {0x07ffffde, 27},
    {0x07ffffdf, 27}, {0x03ffffe5, 26}, {0x00fffff1, 24}, {0x01ffffed, 25},
    {0x0007fff2, 19}, {0x001fffe3, 21}, {0x03ffffe6, 26}, {0x07ffffe0, 27},
    {0x07ffffe1, 27}, {0x03ffffe7, 26}, {0x07ffffe2, 27}, {0x00fffff2, 24},
    {0x001fffe4, 21}, {0x001fffe5, 21}, {0x03ffffe8, 26}, {0x03ffffe9, 26},
    {0x0ffffffd, 28}, {0x07ffffe3, 27}, {0x07ffffe4, 27}, {0x07ffffe5, 27},
    {0x000fffec, 20}, {0x00fffff3, 24}, {0x000fffed, 20}, {0x001fffe6, 21},
    {0x003fffe9, 22}, {0x001fffe7, 21}, {0x001fffe8, 21}, {0x007ffff3, 23},
    {0x003fffea, 22}, {0x003fffeb, 22}, {0x01ffffee, 25}, {0x01ffffef, 25},
    {0x00fffff4, 24}, {0x00fffff5, 24}, {0x03ffffea, 26}, {0x007ffff4, 23},
    {0x03ffffeb, 26}, {0x07ffffe6, 27}, {0x03ffffec, 26}, {0x03ffffed, 26},
    {0x07ffffe7, 27}, {0x07ffffe8, 27}, {0x07ffffe9, 27}, {0x07ffffea, 27},
    {0x07ffffeb, 27}, {0x0ffffffe, 28}, {0x07ffffec, 27}, {0x07ffffed, 27},
    {0x07ffffee, 27}, {0x07ffffef, 27}, {0x07fffff0, 27}, {0x03ffffee, 26}};


/* same as above, but embeds lowercase transformation */
static ngx_http_v2_huff_encode_code_t ngx_http_v2_huff_encode_table_lc[256] = {
    {0x00001ff8, 13}, {0x007fffd8, 23}, {0x0fffffe2, 28}, {0x0fffffe3, 28},
    {0x0fffffe4, 28}, {0x0fffffe5, 28}, {0x0fffffe6, 28}, {0x0fffffe7, 28},
    {0x0fffffe8, 28}, {0x00ffffea, 24}, {0x3ffffffc, 30}, {0x0fffffe9, 28},
    {0x0fffffea, 28}, {0x3ffffffd, 30}, {0x0fffffeb, 28}, {0x0fffffec, 28},
    {0x0fffffed, 28}, {0x0fffffee, 28}, {0x0fffffef, 28}, {0x0ffffff0, 28},
    {0x0ffffff1, 28}, {0x0ffffff2, 28}, {0x3ffffffe, 30}, {0x0ffffff3, 28},
    {0x0ffffff4, 28}, {0x0ffffff5, 28}, {0x0ffffff6, 28}, {0x0ffffff7, 28},
    {0x0ffffff8, 28}, {0x0ffffff9, 28}, {0x0ffffffa, 28}, {0x0ffffffb, 28},
    {0x00000014, 6},  {0x000003f8, 10}, {0x000003f9, 10}, {0x00000ffa, 12},
    {0x00001ff9, 13}, {0x00000015, 6},  {0x000000f8, 8},  {0x000007fa, 11},
    {0x000003fa, 10}, {0x000003fb, 10}, {0x000000f9, 8},  {0x000007fb, 11},
    {0x000000fa, 8},  {0x00000016, 6},  {0x00000017, 6},  {0x00000018, 6},
    {0x00000000, 5},  {0x00000001, 5},  {0x00000002, 5},  {0x00000019, 6},
    {0x0000001a, 6},  {0x0000001b, 6},  {0x0000001c, 6},  {0x0000001d, 6},
    {0x0000001e, 6},  {0x0000001f, 6},  {0x0000005c, 7},  {0x000000fb, 8},
    {0x00007ffc, 15}, {0x00000020, 6},  {0x00000ffb, 12}, {0x000003fc, 10},
    {0x00001ffa, 13}, {0x00000003, 5},  {0x00000023, 6},  {0x00000004, 5},
    {0x00000024, 6},  {0x00000005, 5},  {0x00000025, 6},  {0x00000026, 6},
    {0x00000027, 6},  {0x00000006, 5},  {0x00000074, 7},  {0x00000075, 7},
    {0x00000028, 6},  {0x00000029, 6},  {0x0000002a, 6},  {0x00000007, 5},
    {0x0000002b, 6},  {0x00000076, 7},  {0x0000002c, 6},  {0x00000008, 5},
    {0x00000009, 5},  {0x0000002d, 6},  {0x00000077, 7},  {0x00000078, 7},
    {0x00000079, 7},  {0x0000007a, 7},  {0x0000007b, 7},  {0x00001ffb, 13},
    {0x0007fff0, 19}, {0x00001ffc, 13}, {0x00003ffc, 14}, {0x00000022, 6},
    {0x00007ffd, 15}, {0x00000003, 5},  {0x00000023, 6},  {0x00000004, 5},
    {0x00000024, 6},  {0x00000005, 5},  {0x00000025, 6},  {0x00000026, 6},
    {0x00000027, 6},  {0x00000006, 5},  {0x00000074, 7},  {0x00000075, 7},
    {0x00000028, 6},  {0x00000029, 6},  {0x0000002a, 6},  {0x00000007, 5},
    {0x0000002b, 6},  {0x00000076, 7},  {0x0000002c, 6},  {0x00000008, 5},
    {0x00000009, 5},  {0x0000002d, 6},  {0x00000077, 7},  {0x00000078, 7},
    {0x00000079, 7},  {0x0000007a, 7},  {0x0000007b, 7},  {0x00007ffe, 15},
    {0x000007fc, 11}, {0x00003ffd, 14}, {0x00001ffd, 13}, {0x0ffffffc, 28},
    {0x000fffe6, 20}, {0x003fffd2, 22}, {0x000fffe7, 20}, {0x000fffe8, 20},
    {0x003fffd3, 22}, {0x003fffd4, 22}, {0x003fffd5, 22}, {0x007fffd9, 23},
    {0x003fffd6, 22}, {0x007fffda, 23}, {0x007fffdb, 23}, {0x007fffdc, 23},
    {0x007fffdd, 23}, {0x007fffde, 23}, {0x00ffffeb, 24}, {0x007fffdf, 23},
    {0x00ffffec, 24}, {0x00ffffed, 24}, {0x003fffd7, 22}, {0x007fffe0, 23},
    {0x00ffffee, 24}, {0x007fffe1, 23}, {0x007fffe2, 23}, {0x007fffe3, 23},
    {0x007fffe4, 23}, {0x001fffdc, 21}, {0x003fffd8, 22}, {0x007fffe5, 23},
    {0x003fffd9, 22}, {0x007fffe6, 23}, {0x007fffe7, 23}, {0x00ffffef, 24},
    {0x003fffda, 22}, {0x001fffdd, 21}, {0x000fffe9, 20}, {0x003fffdb, 22},
    {0x003fffdc, 22}, {0x007fffe8, 23}, {0x007fffe9, 23}, {0x001fffde, 21},
    {0x007fffea, 23}, {0x003fffdd, 22}, {0x003fffde, 22}, {0x00fffff0, 24},
    {0x001fffdf, 21}, {0x003fffdf, 22}, {0x007fffeb, 23}, {0x007fffec, 23},
    {0x001fffe0, 21}, {0x001fffe1, 21}, {0x003fffe0, 22}, {0x001fffe2, 21},
    {0x007fffed, 23}, {0x003fffe1, 22}, {0x007fffee, 23}, {0x007fffef, 23},
    {0x000fffea, 20}, {0x003fffe2, 22}, {0x003fffe3, 22}, {0x003fffe4, 22},
    {0x007ffff0, 23}, {0x003fffe5, 22}, {0x003fffe6, 22}, {0x007ffff1, 23},
    {0x03ffffe0, 26}, {0x03ffffe1, 26}, {0x000fffeb, 20}, {0x0007fff1, 19},
    {0x003fffe7, 22}, {0x007ffff2, 23}, {0x003fffe8, 22}, {0x01ffffec, 25},
    {0x03ffffe2, 26}, {0x03ffffe3, 26}, {0x03ffffe4, 26}, {0x07ffffde, 27},
    {0x07ffffdf, 27}, {0x03ffffe5, 26}, {0x00fffff1, 24}, {0x01ffffed, 25},
    {0x0007fff2, 19}, {0x001fffe3, 21}, {0x03ffffe6, 26}, {0x07ffffe0, 27},
    {0x07ffffe1, 27}, {0x03ffffe7, 26}, {0x07ffffe2, 27}, {0x00fffff2, 24},
    {0x001fffe4, 21}, {0x001fffe5, 21}, {0x03ffffe8, 26}, {0x03ffffe9, 26},
    {0x0ffffffd, 28}, {0x07ffffe3, 27}, {0x07ffffe4, 27}, {0x07ffffe5, 27},
    {0x000fffec, 20}, {0x00fffff3, 24}, {0x000fffed, 20}, {0x001fffe6, 21},
    {0x003fffe9, 22}, {0x001fffe7, 21}, {0x001fffe8, 21}, {0x007ffff3, 23},
    {0x003fffea, 22}, {0x003fffeb, 22}, {0x01ffffee, 25}, {0x01ffffef, 25},
    {0x00fffff4, 24}, {0x00fffff5, 24}, {0x03ffffea, 26}, {0x007ffff4, 23},
    {0x03ffffeb, 26}, {0x07ffffe6, 27}, {0x03ffffec, 26}, {0x03ffffed, 26},
    {0x07ffffe7, 27}, {0x07ffffe8, 27}, {0x07ffffe9, 27}, {0x07ffffea, 27},
    {0x07ffffeb, 27}, {0x0ffffffe, 28}, {0x07ffffec, 27}, {0x07ffffed, 27},
    {0x07ffffee, 27}, {0x07ffffef, 27}, {0x07fffff0, 27}, {0x03ffffee, 26}};


#if (NGX_PTR_SIZE == 8)

#if (NGX_HAVE_LITTLE_ENDIAN)

#if (NGX_HAVE_GCC_BSWAP64)
#define ngx_http_v2_huff_encode_buf(dst, buf) \
    (*(uint64_t *)(dst) = __builtin_bswap64(buf))
#else
#define ngx_http_v2_huff_encode_buf(dst, buf)                            \
    ((dst)[0] = (u_char)((buf) >> 56), (dst)[1] = (u_char)((buf) >> 48), \
     (dst)[2] = (u_char)((buf) >> 40), (dst)[3] = (u_char)((buf) >> 32), \
     (dst)[4] = (u_char)((buf) >> 24), (dst)[5] = (u_char)((buf) >> 16), \
     (dst)[6] = (u_char)((buf) >> 8), (dst)[7] = (u_char)(buf))
#endif

#else /* !NGX_HAVE_LITTLE_ENDIAN */
#define ngx_http_v2_huff_encode_buf(dst, buf) (*(uint64_t *)(dst) = (buf))
#endif

#else /* NGX_PTR_SIZE == 4 */

#define ngx_http_v2_huff_encode_buf(dst, buf) (*(uint32_t *)(dst) = htonl(buf))

#endif


size_t
ngx_http_v2_huff_encode(u_char *src, size_t len, u_char *dst, ngx_uint_t lower)
{
    u_char                         *end;
    size_t                          hlen;
    ngx_uint_t                      buf, pending, code;
    ngx_http_v2_huff_encode_code_t *table, *next;

    table   = lower ? ngx_http_v2_huff_encode_table_lc
                    : ngx_http_v2_huff_encode_table;
    hlen    = 0;
    buf     = 0;
    pending = 0;

    end = src + len;

    while (src != end)
    {
        next = &table[*src++];

        code = next->code;
        pending += next->len;

        /* accumulate bits */
        if (pending < sizeof(buf) * 8)
        {
            buf |= code << (sizeof(buf) * 8 - pending);
            continue;
        }

        if (hlen + sizeof(buf) >= len)
        {
            return 0;
        }

        pending -= sizeof(buf) * 8;

        buf |= code >> pending;

        ngx_http_v2_huff_encode_buf(&dst[hlen], buf);

        hlen += sizeof(buf);

        buf = pending ? code << (sizeof(buf) * 8 - pending) : 0;
    }

    if (pending == 0)
    {
        return hlen;
    }

    buf |= (ngx_uint_t)-1 >> pending;

    pending = ngx_align(pending, 8);

    if (hlen + pending / 8 >= len)
    {
        return 0;
    }

    buf >>= sizeof(buf) * 8 - pending;

    do
    {
        pending -= 8;
        dst[hlen++] = (u_char)(buf >> pending);
    } while (pending);

    return hlen;
}
